The objective or the proposed research is to identify and map cellular genes which may be involved in the expression of the transformation phenotype in human and mouse cells. Transformed cell lines of human and mouse origin with dominant and recessive expression of transformation will be identified first by cell/cell hybridization in intra-specific combination. We will then utilize DNA Mediated Gene Transfer (DMT), Chromosome Mediated Gene Transfer (CMGT) and Microcell fusion techniques to transfer defined amounts of genetic material between transformed and normal cells in interspecies combination for the genetic analysis. Our experimental approach involves the following: When transformation phenotype is dominant, microcells, metaphase chromosomes or DNA prepared from the transformed cells will be transferred to normal cells in interspecies combination. The genome transfer colonies isolated by a parameter of transformation such as growth in agar will be subjected to cytological and biochemical analysis. In another set of experiments, we will first integrate a selectable marker (hamster hypoxanthine phosphoribosytransferase; hprt gene or E. coli xanthine phosphoribosyl transferase; xprt) into the chromosomes of transformed and normal cells by CMGT or DMT to isolate a bank of cell lines, each carrying the selectable marker integrated in to a different chromosome. Microcells prepared from these clonal cell lines expressing transferred hprt gene will be fused in interspecies combination as follows: 1) When transformation is dominant: microcells from transformed hprt+ cells x normal hprt- cells. 2) When transformation is recessive: microcells from normal hprt+ cells x transformed hprt- cells. The resultant microcell hybrids will be isolated by selection in agar + HAT (hypoxanthine, amethopterine, thymidine) and HAT respectively and analyzed to obtain the following information. (1) Expression of transformation phenotype. (2) Number and identity of chromosomes required for the expression or suppression of transformation. (3) Number and chromosomal location of genes and their linkage relationships. A concordant loss of chromosome(s) and transformed or normal phenotype will be demonstrated in subclones of microcell hybrids selected in 6-thioguanine.